The present invention relates to a method of pattern formation and making a semiconductor using a radiation-induced conductive resin bottom-resist layer.
In making a highly integrated circuit, the so-called multi-layer resist process is employed. In the multi-layer resist process, an organic resin having a high dry etching resistance is used as a bottom-resist layer to smooth the surface to be processed and to increase the dry etching resistance of the surface. However, most of the prior organic resin layers are insulators, i.e., non-conducting. As a result, when the non-conducting organic resin bottom-resist layer is exposed to an electron beam exposure during the patterning step, an electrical charge is accumulated in the bottom-resist layer. This causes a turbulence of the electric field on the surface of the substrate. Accordingly, a highly accurate pattern cannot be obtained.
Attempts have been made in the past to reduce this charge accumulation by using a bottom-resist layer having a mixture of a synthetic resin superior in dry etching resistance and a complex salt of a polycation polymer, known as a conductive polymer, and tetracyanoquinodimethane (Japanese Patent Kokai No. 62-113135). Since the bottom layer must have a sufficient dry etching resistance and the conductive polymer alone cannot be used as a bottom-resist layer, the conductive polymer is mixed with the synthetic resin superior in dry etching resistance to simply improve the conductivity.
However, the conductivity of the bottom-resist layer composition obtained by the above process ranges only from 10.sup.12 to 10.sup.15 S.cm.sup.-1, which is nearly the same as that of a silicate glass known as an insulator. Thus, the improvement is considerably limited.
The prior art bottom-resist layer accordingly does not possess ideal properties, namely, the properties of both the high dry etching resistance and the conductivity.